The present invention relates to a general signaling service unit in time-division electronic switching system, and more particularly, to a general signaling service unit for providing a signal required to connection and progress of calling in electronic switching system.
Various signaling service functions for controlling the connection and progress of calling are used in variety among the service functions of electronic switching system, and signaling service unit for providing these signaling service functions is necessarily required to realize the essential function of electronic switching system which is connection of channel.
Among the signaling service functions of electronic switching system, there is transmitting and receiving function of R2 MFC (R2 multi-frequency compelled) signal used for the information exchange between telephone exchanges in channel associated signaling method in which signal is exchanged through relay line channel, and further receiving function of DTMF (dual tone multi-frequency) signal from push button telephone subscriber as well as transmitting junction of various audible signal tone for informing the connecting and progressing state of calling from switching system to telephone, are mainly handled, and in addition to these, transmitting and receiving function of CCT (continuity checking tone) for confirming whether or not it being normal with respect to the relay line channel between telephone exchanges is also used in accordance with the common channel signaling method being used in which signal exchange between telephone exchanges is executed through common exclusive signal channel separate from the relay line channel as a signaling method between telephone exchanges.
Signaling service unit executing respectively the functions of R2 MFC signal transmitting and receiving, DTMF signal transmitting and receiving, audible signal tone transmitting, and continuity checking tone transmitting and receiving which are used for processing of calling in electronic switching system, is normally provided by way of switch network to the subscriber's line or relay line, and in conventional electronic switching system (refer to following reference materials), in accordance with the kind of channel applied by each kind of signaling service, location serviced by multiplying and providing form of service, controlling method of signaling service unit, is constituted with respective forms and being complicated as a whole, and since signaling service unit is constituted with separated forms and being made of several kinds of circuit packs, occupying area of signaling service unit within the electronic switching system is increased and reliability is decreased, so that not only the maintenance and management are difficult but also there has been many disadvantages in view point of productivity and economism.
On the other hand, in accordance with the recent development of digital signal processing technique and semiconductor integrating circuit technique, digital signal processor chip DSP for digital signal processing only is developed, so that development of signaling service unit of high performance for generating and detecting the digital signal has become possible, and constitution of multi-function type signaling service unit for transmitting and receiving various kinds of signals by using DSP chip has also become possible.